1. Field of the Invention
The present invention relates to a paper sheet processing apparatus which inspects paper sheets such as securities and bundles them by paper bands in accordance with kinds, and inspects the bundled states of paper sheets and discharges the bundles of paper sheets.
2. Description of the Related Art
There is known a conventional paper sheet processing apparatus which processes paper sheets such as securities. A plurality of paper sheets to be processed are input as a batch, and the input paper sheets are transferred along a transfer path one by one. The quality (shape, degree of damage, print state, stain, etc.) of each paper sheet, which is transferred, is inspected, and paper sheets that are determined to be circulatable by the inspection result (hereinafter referred to as “valid notes”), paper sheets that are determined to be non-circulatable by the inspection result (hereinafter referred to as “invalid notes”) and paper sheets that are treated as samples for human inspection (hereinafter referred to as “audit notes”) are sorted and stacked in sorting sections to which these paper sheets are assigned.
This apparatus includes a plurality of bundling sections which bundle the valid notes, invalid notes and audit notes, which are sorted and stacked in the sorting sections in accordance with the inspection result, as described above, in units of, e.g. 100 notes by paper bands. The bundles which are obtained by the bundling sections are discharged to the outside of the apparatus via a common conveyor. The conveyor is provided to extend under the bundling sections along the direction of arrangement of the bundling sections.
In this apparatus, when the bundles are discharged from the apparatus via the conveyor, the length of the bundle in the direction of conveyance of the bundle is detected and compared with a reference value, and a bundle in an unwanted bundled state is rejected. For example, in an apparatus that is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-73353, the time of passage of the bundle, which is conveyed at a constant speed, is detected by using two transmission sensors which are spaced apart in a direction perpendicular to the direction of conveyance of the bundle. The detected time of passage is measured by using fixed clock pulses, and compared with a preset reference value. Thereby, abnormality in the length of the bundle in the direction of conveyance is detected.
For example, in a case where the speed V of conveyance of the bundle by the conveyor is 666 [mm/s] and the length Ls of the bundle in the direction of conveyance is 160 [mm], the time T [s] during which the transmission sensors detect the bundle is expressed byT=Ls/V=0.240 [s]=240 [ms].
If the time T [s] is measured by using clock pulses CK of, e.g. 1 [ms] cycle, the measured value Lc is given byLc=T/CK=240 [ms]/1 [ms]=240.Thus, abnormality in the length of the bundle can be detected by comparing the measured value Lc with a reference value.
At this time, the precision of measurement of the length of the bundle becomes higher as the measured value Lc for the detection of the bundle is higher, and the precision of measurement varies depending on the distance Ac of movement of the bundle during one clock pulse, i.e.Ac=V×CK=0.666 [mm].In other words, the precision of measurement becomes higher as the distance Ac of movement in one clock pulse is shorter.
Although the precision of measurement can be enhanced by decreasing the speed of conveyance of the bundle by the conveyor, the processing performance of the apparatus as a whole deteriorates if the speed of the conveyor is lowered. In usual cases, in consideration of the processing performance of the apparatus, the speed of conveyance of the conveyor is set at a maximum value within such a range that bundles that are formed by bundling sections can normally be conveyed to the outside of the apparatus.
In order to enhance the precision of measurement while maintaining the speed of conveyance of the bundle by the conveyor, it is thinkable to shorten the cycle of the above-mentioned clock pulse CK. In this method, however, such a problem arises that the load on the system, which is needed for arithmetic operations, increases.